153-418: Metabolism ( / m ə ˈ t æ b ə l ɪ z ə m / , from Greek : μεταβολή metabolē , "change") is the set of life -sustaining chemical reactions in organisms . The three main functions of metabolism are: the conversion of the energy in food to energy available to run cellular processes; the conversion of food to building blocks of proteins , lipids , nucleic acids , and some carbohydrates ; and
306-463: A futile cycle . Although fat is a common way of storing energy, in vertebrates such as humans the fatty acids in these stores cannot be converted to glucose through gluconeogenesis as these organisms cannot convert acetyl-CoA into pyruvate ; plants do, but animals do not, have the necessary enzymatic machinery. As a result, after long-term starvation, vertebrates need to produce ketone bodies from fatty acids to replace glucose in tissues such as
459-416: A ketone ), the glycerol component of triglycerides can be converted into glucose , via gluconeogenesis by conversion into dihydroxyacetone phosphate and then into glyceraldehyde 3-phosphate , for brain fuel when it is broken down. Fat cells may also be broken down for that reason if the brain's needs ever outweigh the body's. Triglycerides cannot pass through cell membranes freely. Special enzymes on
612-438: A DNA template from its viral RNA genome. RNA in ribozymes such as spliceosomes and ribosomes is similar to enzymes as it can catalyze chemical reactions. Individual nucleosides are made by attaching a nucleobase to a ribose sugar. These bases are heterocyclic rings containing nitrogen, classified as purines or pyrimidines . Nucleotides also act as coenzymes in metabolic-group-transfer reactions. Metabolism involves
765-570: A basis for coinages: anthropology , photography , telephony , isomer , biomechanics , cinematography , etc. Together with Latin words , they form the foundation of international scientific and technical vocabulary ; for example, all words ending in -logy ('discourse'). There are many English words of Greek origin . Greek is an independent branch of the Indo-European language family. The ancient language most closely related to it may be ancient Macedonian , which, by most accounts,
918-420: A constant set of conditions within cells, a condition called homeostasis . Metabolic regulation also allows organisms to respond to signals and interact actively with their environments. Two closely linked concepts are important for understanding how metabolic pathways are controlled. Firstly, the regulation of an enzyme in a pathway is how its activity is increased and decreased in response to signals. Secondly,
1071-428: A cycle of reactions that add the acyl group, reduce it to an alcohol, dehydrate it to an alkene group and then reduce it again to an alkane group. The enzymes of fatty acid biosynthesis are divided into two groups: in animals and fungi, all these fatty acid synthase reactions are carried out by a single multifunctional type I protein, while in plant plastids and bacteria separate type II enzymes perform each step in
1224-422: A decreased risk of certain cancers, including breast and colorectal cancer, while other studies found no associations with cancer risk. Polyunsaturated fat supplementation was found to have no effect on the incidence of pregnancy-related disorders, such as hypertension or preeclampsia , but may increase the length of gestation slightly and decreased the incidence of early premature births. Expert panels in
1377-552: A fairly stable set of consonantal contrasts . The main phonological changes occurred during the Hellenistic and Roman period (see Koine Greek phonology for details): In all its stages, the morphology of Greek shows an extensive set of productive derivational affixes , a limited but productive system of compounding and a rich inflectional system. Although its morphological categories have been fairly stable over time, morphological changes are present throughout, particularly in
1530-556: A faster, more convenient cursive writing style with the use of ink and quill . The Greek alphabet consists of 24 letters, each with an uppercase ( majuscule ) and lowercase ( minuscule ) form. The letter sigma has an additional lowercase form (ς) used in the final position of a word: In addition to the letters, the Greek alphabet features a number of diacritical signs : three different accent marks ( acute , grave , and circumflex ), originally denoting different shapes of pitch accent on
1683-531: A foreign language. It is also often stated that the historical changes have been relatively slight compared with some other languages. According to one estimation, " Homeric Greek is probably closer to Demotic than 12-century Middle English is to modern spoken English ". Greek is spoken today by at least 13 million people, principally in Greece and Cyprus along with a sizable Greek-speaking minority in Albania near
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#17329063123601836-507: A higher proportion of unsaturated acids, although there are exceptions such as coconut oil and palm kernel oil . Foods containing unsaturated fats include avocado , nuts , olive oils , and vegetable oils such as canola . Many scientific studies have found that replacing saturated fats with cis unsaturated fats in the diet reduces risk of cardiovascular diseases (CVDs), diabetes , or death. These studies prompted many medical organizations and public health departments, including
1989-454: A hydrogen acceptor. Hundreds of separate types of dehydrogenases remove electrons from their substrates and reduce NAD into NADH. This reduced form of the coenzyme is then a substrate for any of the reductases in the cell that need to transfer hydrogen atoms to their substrates. Nicotinamide adenine dinucleotide exists in two related forms in the cell, NADH and NADPH. The NAD/NADH form is more important in catabolic reactions, while NADP/NADPH
2142-501: A large fraction of the population in developing countries. Concerns were also expressed at a 2010 conference of the American Dietetic Association that a blanket recommendation to avoid saturated fats could drive people to also reduce the amount of polyunsaturated fats, which may have health benefits, and/or replace fats by refined carbohydrates — which carry a high risk of obesity and heart disease. For these reasons,
2295-556: A large group of compounds that contain fatty acids and glycerol ; a glycerol molecule attached to three fatty acids by ester linkages is called a triacylglyceride . Several variations of the basic structure exist, including backbones such as sphingosine in sphingomyelin , and hydrophilic groups such as phosphate in phospholipids . Steroids such as sterol are another major class of lipids. Carbohydrates are aldehydes or ketones , with many hydroxyl groups attached, that can exist as straight chains or rings. Carbohydrates are
2448-402: A larger increase in the entropy of their environments. The metabolism of a cell achieves this by coupling the spontaneous processes of catabolism to the non-spontaneous processes of anabolism. In thermodynamic terms, metabolism maintains order by creating disorder. As the environments of most organisms are constantly changing, the reactions of metabolism must be finely regulated to maintain
2601-469: A membrane. Pumping protons out of the mitochondria creates a proton concentration difference across the membrane and generates an electrochemical gradient . This force drives protons back into the mitochondrion through the base of an enzyme called ATP synthase . The flow of protons makes the stalk subunit rotate, causing the active site of the synthase domain to change shape and phosphorylate adenosine diphosphate —turning it into ATP. Chemolithotrophy
2754-419: A mixture of such compounds , most commonly those that occur in living beings or in food . The term often refers specifically to triglycerides (triple esters of glycerol ), that are the main components of vegetable oils and of fatty tissue in animals; or, even more narrowly, to triglycerides that are solid or semisolid at room temperature, thus excluding oils . The term may also be used more broadly as
2907-405: A process called lipolysis . They are subsequently moved to absorptive enterocyte cells lining the intestines. The triglycerides are rebuilt in the enterocytes from their fragments and packaged together with cholesterol and proteins to form chylomicrons . These are excreted from the cells and collected by the lymph system and transported to the large vessels near the heart before being mixed into
3060-588: A set of xenobiotic-metabolizing enzymes. In humans, these include cytochrome P450 oxidases , UDP-glucuronosyltransferases , and glutathione S -transferases . This system of enzymes acts in three stages to firstly oxidize the xenobiotic (phase I) and then conjugate water-soluble groups onto the molecule (phase II). The modified water-soluble xenobiotic can then be pumped out of cells and in multicellular organisms may be further metabolized before being excreted (phase III). In ecology , these reactions are particularly important in microbial biodegradation of pollutants and
3213-458: A short ancestral pathway, the duplication and then divergence of entire pathways as well as the recruitment of pre-existing enzymes and their assembly into a novel reaction pathway. The relative importance of these mechanisms is unclear, but genomic studies have shown that enzymes in a pathway are likely to have a shared ancestry, suggesting that many pathways have evolved in a step-by-step fashion with novel functions created from pre-existing steps in
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#17329063123603366-423: A significant relationship between saturated fat and high serum cholesterol levels, which in turn have been claimed to have a causal relation with increased risk of cardiovascular disease (the so-called lipid hypothesis ). However, high cholesterol may be caused by many factors. Other indicators, such as high LDL/HDL ratio, have proved to be more predictive. In a study of myocardial infarction in 52 countries,
3519-527: A source of energy, while switching between carbon fixation and the fermentation of organic compounds. In many organisms, the capture of solar energy is similar in principle to oxidative phosphorylation, as it involves the storage of energy as a proton concentration gradient. This proton motive force then drives ATP synthesis. The electrons needed to drive this electron transport chain come from light-gathering proteins called photosynthetic reaction centres . Reaction centers are classified into two types depending on
3672-506: A synonym of lipid —any substance of biological relevance, composed of carbon , hydrogen , or oxygen , that is insoluble in water but soluble in non-polar solvents . In this sense, besides the triglycerides, the term would include several other types of compounds like mono- and diglycerides , phospholipids (such as lecithin ), sterols (such as cholesterol ), waxes (such as beeswax ), and free fatty acids, which are usually present in human diet in smaller amounts. Fats are one of
3825-411: A vast array of chemical reactions, but most fall under a few basic types of reactions that involve the transfer of functional groups of atoms and their bonds within molecules. This common chemistry allows cells to use a small set of metabolic intermediates to carry chemical groups between different reactions. These group-transfer intermediates are called coenzymes . Each class of group-transfer reactions
3978-503: A vital role in maintaining healthy skin and hair , insulating body organs against shock, maintaining body temperature, and promoting healthy cell function. Fat also serves as a useful buffer against a host of diseases. When a particular substance, whether chemical or biotic, reaches unsafe levels in the bloodstream, the body can effectively dilute—or at least maintain equilibrium of—the offending substances by storing it in new fat tissue. This helps to protect vital organs, until such time as
4131-466: A water molecule H 2 O . Other less common types of fats include diglycerides and monoglycerides , where the esterification is limited to two or just one of glycerol's –OH groups. Other alcohols, such as cetyl alcohol (predominant in spermaceti ), may replace glycerol. In the phospholipids , one of the fatty acids is replaced by phosphoric acid or a monoester thereof. The benefits and risks of various amounts and types of dietary fats have been
4284-551: A weak atherogenic effect. Different saturated fatty acids have differing effects on various lipid levels. The evidence for a relation between saturated fat intake and cancer is significantly weaker, and there does not seem to be a clear medical consensus about it. Various animal studies have indicated that the intake of saturated fat has a negative effect on the mineral density of bones . One study suggested that men may be particularly vulnerable. Studies have shown that substituting monounsaturated fatty acids for saturated ones
4437-415: Is oxidative stress . Here, processes including oxidative phosphorylation and the formation of disulfide bonds during protein folding produce reactive oxygen species such as hydrogen peroxide . These damaging oxidants are removed by antioxidant metabolites such as glutathione and enzymes such as catalases and peroxidases . Living organisms must obey the laws of thermodynamics , which describe
4590-448: Is a triglyceride , an ester of the triple alcohol glycerol H(–CHOH–) 3 H and three fatty acids. The molecule of a triglyceride can be described as resulting from a condensation reaction (specifically, esterification ) between each of glycerol's –OH groups and the HO– part of the carboxyl group HO(O=)C− of each fatty acid, forming an ester bridge −O−(O=)C− with elimination of
4743-564: Is a type of metabolism found in prokaryotes where energy is obtained from the oxidation of inorganic compounds . These organisms can use hydrogen , reduced sulfur compounds (such as sulfide , hydrogen sulfide and thiosulfate ), ferrous iron (Fe(II)) or ammonia as sources of reducing power and they gain energy from the oxidation of these compounds. These microbial processes are important in global biogeochemical cycles such as acetogenesis , nitrification and denitrification and are critical for soil fertility . The energy in sunlight
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4896-741: Is about 75% monounsaturated fat. The high oleic variety sunflower oil contains at least 70% monounsaturated fat. Canola oil and cashews are both about 58% monounsaturated fat. Tallow (beef fat) is about 50% monounsaturated fat, and lard is about 40% monounsaturated fat. Other sources include hazelnut , avocado oil , macadamia nut oil , grapeseed oil , groundnut oil ( peanut oil ), sesame oil , corn oil , popcorn , whole grain wheat , cereal , oatmeal , almond oil , hemp oil , and tea-oil camellia . Polyunsaturated fatty acids can be found mostly in nuts, seeds, fish, seed oils, and oysters . Food sources of polyunsaturated fats include: MUFAs (especially oleic acid) have been found to lower
5049-766: Is also found in Bulgaria near the Greek-Bulgarian border. Greek is also spoken worldwide by the sizable Greek diaspora which has notable communities in the United States , Australia , Canada , South Africa , Chile , Brazil , Argentina , Russia , Ukraine , the United Kingdom , and throughout the European Union , especially in Germany . Historically, significant Greek-speaking communities and regions were found throughout
5202-742: Is an Indo-European language, constituting an independent Hellenic branch within the Indo-European language family. It is native to Greece , Cyprus , Italy (in Calabria and Salento ), southern Albania , and other regions of the Balkans , Caucasus , the Black Sea coast, Asia Minor , and the Eastern Mediterranean . It has the longest documented history of any Indo-European language, spanning at least 3,400 years of written records. Its writing system
5355-474: Is an Indo-European language, but also includes a number of borrowings from the languages of the populations that inhabited Greece before the arrival of Proto-Greeks, some documented in Mycenaean texts ; they include a large number of Greek toponyms . The form and meaning of many words have changed. Loanwords (words of foreign origin) have entered the language, mainly from Latin, Venetian , and Turkish . During
5508-399: Is an organic compound needed in small quantities that cannot be made in cells. In human nutrition , most vitamins function as coenzymes after modification; for example, all water-soluble vitamins are phosphorylated or are coupled to nucleotides when they are used in cells. Nicotinamide adenine dinucleotide (NAD), a derivative of vitamin B 3 ( niacin ), is an important coenzyme that acts as
5661-459: Is associated with increased daily physical activity and resting energy expenditure. More physical activity, less anger, and less irritability were associated with a higher-oleic acid diet than one of a palmitic acid diet. The most common fatty acids in human diet are unsaturated or mono-unsaturated. Monounsaturated fats are found in animal flesh such as red meat , whole milk products, nuts, and high fat fruits such as olives and avocados. Olive oil
5814-445: Is called gluconeogenesis . Gluconeogenesis converts pyruvate to glucose-6-phosphate through a series of intermediates, many of which are shared with glycolysis . However, this pathway is not simply glycolysis run in reverse, as several steps are catalyzed by non-glycolytic enzymes. This is important as it allows the formation and breakdown of glucose to be regulated separately, and prevents both pathways from running simultaneously in
5967-409: Is captured by plants , cyanobacteria , purple bacteria , green sulfur bacteria and some protists . This process is often coupled to the conversion of carbon dioxide into organic compounds, as part of photosynthesis, which is discussed below. The energy capture and carbon fixation systems can, however, operate separately in prokaryotes, as purple bacteria and green sulfur bacteria can use sunlight as
6120-404: Is carried out by a particular coenzyme, which is the substrate for a set of enzymes that produce it, and a set of enzymes that consume it. These coenzymes are therefore continuously made, consumed and then recycled. One central coenzyme is adenosine triphosphate (ATP), the energy currency of cells. This nucleotide is used to transfer chemical energy between different chemical reactions. There
6273-636: Is carried out by the enzyme RuBisCO as part of the Calvin–Benson cycle . Three types of photosynthesis occur in plants, C3 carbon fixation , C4 carbon fixation and CAM photosynthesis . These differ by the route that carbon dioxide takes to the Calvin cycle, with C3 plants fixing CO 2 directly, while C4 and CAM photosynthesis incorporate the CO 2 into other compounds first, as adaptations to deal with intense sunlight and dry conditions. In photosynthetic prokaryotes
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6426-484: Is composed of a phosphate attached to a ribose or deoxyribose sugar group which is attached to a nitrogenous base . Nucleic acids are critical for the storage and use of genetic information, and its interpretation through the processes of transcription and protein biosynthesis . This information is protected by DNA repair mechanisms and propagated through DNA replication . Many viruses have an RNA genome , such as HIV , which uses reverse transcription to create
6579-603: Is contrary to the suggestion that polyunsaturated fats are shown to be protective against insulin resistance. The large scale KANWU study found that increasing MUFA and decreasing SFA intake could improve insulin sensitivity, but only when the overall fat intake of the diet was low. However, some MUFAs may promote insulin resistance (like the SFAs), whereas PUFAs may protect against it. Levels of oleic acid along with other MUFAs in red blood cell membranes were positively associated with breast cancer risk. The saturation index (SI) of
6732-476: Is its primary structure . Just as the letters of the alphabet can be combined to form an almost endless variety of words, amino acids can be linked in varying sequences to form a huge variety of proteins. Proteins are made from amino acids that have been activated by attachment to a transfer RNA molecule through an ester bond. This aminoacyl-tRNA precursor is produced in an ATP -dependent reaction carried out by an aminoacyl tRNA synthetase . This aminoacyl-tRNA
6885-631: Is likely due to their efficacy . In various diseases, such as type II diabetes , metabolic syndrome , and cancer , normal metabolism is disrupted. The metabolism of cancer cells is also different from the metabolism of normal cells, and these differences can be used to find targets for therapeutic intervention in cancer. Most of the structures that make up animals, plants and microbes are made from four basic classes of molecules : amino acids , carbohydrates , nucleic acid and lipids (often called fats ). As these molecules are vital for life, metabolic reactions either focus on making these molecules during
7038-557: Is needed, or back to glucose in the Cori cycle . An alternative route for glucose breakdown is the pentose phosphate pathway , which produces less energy but supports anabolism (biomolecule synthesis). This pathway reduces the coenzyme NADP to NADPH and produces pentose compounds such as ribose 5-phosphate for synthesis of many biomolecules such as nucleotides and aromatic amino acids . Fats are catabolized by hydrolysis to free fatty acids and glycerol. The glycerol enters glycolysis and
7191-473: Is only a small amount of ATP in cells, but as it is continuously regenerated, the human body can use about its own weight in ATP per day. ATP acts as a bridge between catabolism and anabolism . Catabolism breaks down molecules, and anabolism puts them together. Catabolic reactions generate ATP, and anabolic reactions consume it. It also serves as a carrier of phosphate groups in phosphorylation reactions. A vitamin
7344-521: Is partially modulated by dietary fat ratios ( omega−3 / 6 / 9 ) with both omega−3 and −9 thought to be anti-inflammatory, and omega−6 pro-inflammatory (as well as by numerous other dietary components, particularly polyphenols and exercise, with both of these anti-inflammatory). Although both pro- and anti-inflammatory types of fat are biologically necessary, fat dietary ratios in most US diets are skewed towards omega−6, with subsequent disinhibition of inflammation and potentiation of insulin resistance. This
7497-410: Is produced in response to rises in blood glucose levels . Binding of the hormone to insulin receptors on cells then activates a cascade of protein kinases that cause the cells to take up glucose and convert it into storage molecules such as fatty acids and glycogen . The metabolism of glycogen is controlled by activity of phosphorylase , the enzyme that breaks down glycogen, and glycogen synthase ,
7650-510: Is protected and promoted officially as a regional and minority language in Armenia, Hungary , Romania, and Ukraine. It is recognized as a minority language and protected in Turkey by the 1923 Treaty of Lausanne . The phonology , morphology , syntax , and vocabulary of the language show both conservative and innovative tendencies across the entire attestation of the language from the ancient to
7803-543: Is scarce, or when cells undergo metabolic stress. Lipids are the most diverse group of biochemicals. Their main structural uses are as part of internal and external biological membranes , such as the cell membrane . Their chemical energy can also be used. Lipids contain a long, non-polar hydrocarbon chain with a small polar region containing oxygen. Lipids are usually defined as hydrophobic or amphipathic biological molecules but will dissolve in organic solvents such as ethanol , benzene or chloroform . The fats are
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#17329063123607956-835: Is sometimes called aljamiado , as when Romance languages are written in the Arabic alphabet. Article 1 of the Universal Declaration of Human Rights in Greek: Transcription of the example text into Latin alphabet : Article 1 of the Universal Declaration of Human Rights in English: Proto-Greek Mycenaean Ancient Koine Medieval Modern Fat In nutrition , biology , and chemistry , fat usually means any ester of fatty acids , or
8109-518: Is spoken by at least 13.5 million people today in Greece, Cyprus, Italy, Albania, Turkey , and the many other countries of the Greek diaspora . Greek roots have been widely used for centuries and continue to be widely used to coin new words in other languages; Greek and Latin are the predominant sources of international scientific vocabulary . Greek has been spoken in the Balkan peninsula since around
8262-758: Is still used internationally for the writing of Ancient Greek . In Greek, the question mark is written as the English semicolon, while the functions of the colon and semicolon are performed by a raised point (•), known as the ano teleia ( άνω τελεία ). In Greek the comma also functions as a silent letter in a handful of Greek words, principally distinguishing ό,τι ( ó,ti , 'whatever') from ότι ( óti , 'that'). Ancient Greek texts often used scriptio continua ('continuous writing'), which means that ancient authors and scribes would write word after word with no spaces or punctuation between words to differentiate or mark boundaries. Boustrophedon , or bi-directional text,
8415-630: Is the Greek alphabet , which has been used for approximately 2,800 years; previously, Greek was recorded in writing systems such as Linear B and the Cypriot syllabary . The alphabet arose from the Phoenician script and was in turn the basis of the Latin , Cyrillic , Coptic , Gothic , and many other writing systems. The Greek language holds a very important place in the history of the Western world. Beginning with
8568-615: Is the measure of the amount of energy consumed by all of these chemical reactions. A striking feature of metabolism is the similarity of the basic metabolic pathways among vastly different species. For example, the set of carboxylic acids that are best known as the intermediates in the citric acid cycle are present in all known organisms, being found in species as diverse as the unicellular bacterium Escherichia coli and huge multicellular organisms like elephants . These similarities in metabolic pathways are likely due to their early appearance in evolutionary history , and their retention
8721-422: Is the synthesis of carbohydrates from sunlight and carbon dioxide (CO 2 ). In plants, cyanobacteria and algae, oxygenic photosynthesis splits water, with oxygen produced as a waste product. This process uses the ATP and NADPH produced by the photosynthetic reaction centres , as described above, to convert CO 2 into glycerate 3-phosphate , which can then be converted into glucose. This carbon-fixation reaction
8874-490: Is then a substrate for the ribosome , which joins the amino acid onto the elongating protein chain, using the sequence information in a messenger RNA . Nucleotides are made from amino acids, carbon dioxide and formic acid in pathways that require large amounts of metabolic energy. Consequently, most organisms have efficient systems to salvage preformed nucleotides. Purines are synthesized as nucleosides (bases attached to ribose ). Both adenine and guanine are made from
9027-423: Is transformed through a series of steps into another chemical, each step being facilitated by a specific enzyme . Enzymes are crucial to metabolism because they allow organisms to drive desirable reactions that require energy and will not occur by themselves, by coupling them to spontaneous reactions that release energy. Enzymes act as catalysts —they allow a reaction to proceed more rapidly—and they also allow
9180-428: Is used in anabolic reactions. Inorganic elements play critical roles in metabolism; some are abundant (e.g. sodium and potassium ) while others function at minute concentrations. About 99% of a human's body weight is made up of the elements carbon , nitrogen , calcium , sodium , chlorine , potassium , hydrogen , phosphorus , oxygen and sulfur . Organic compounds (proteins, lipids and carbohydrates) contain
9333-501: The ApoB / ApoA1 (related to LDL and HDL, respectively) ratio was the strongest predictor of CVD among all risk factors. There are other pathways involving obesity , triglyceride levels, insulin sensitivity , endothelial function , and thrombogenicity , among others, that play a role in CVD, although it seems, in the absence of an adverse blood lipid profile, the other known risk factors have only
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#17329063123609486-486: The Eastern Mediterranean , in what are today Southern Italy , Turkey , Cyprus , Syria , Lebanon , Israel , Palestine , Egypt , and Libya ; in the area of the Black Sea , in what are today Turkey, Bulgaria , Romania , Ukraine , Russia , Georgia , Armenia , and Azerbaijan ; and, to a lesser extent, in the Western Mediterranean in and around colonies such as Massalia , Monoikos , and Mainake . It
9639-510: The Indo-Iranian languages (see Graeco-Aryan ), but little definitive evidence has been found. In addition, Albanian has also been considered somewhat related to Greek and Armenian, and it has been proposed that they all form a higher-order subgroup along with other extinct languages of the ancient Balkans; this higher-order subgroup is usually termed Palaeo-Balkan , and Greek has a central position in it. Linear B , attested as early as
9792-460: The Mediterranean Sea area, includes more total fat than the diet of Northern European countries, but most of it is in the form of unsaturated fatty acids (specifically, monounsaturated and omega-3) from olive oil and fish, vegetables, and certain meats like lamb, while consumption of saturated fat is minimal in comparison. A 2017 review found evidence that a Mediterranean-style diet could reduce
9945-469: The World Health Organization (WHO), to officially issue that advice. Some countries with such recommendations include: A 2004 review concluded that "no lower safe limit of specific saturated fatty acid intakes has been identified" and recommended that the influence of varying saturated fatty acid intakes against a background of different individual lifestyles and genetic backgrounds should be
10098-424: The bioremediation of contaminated land and oil spills. Many of these microbial reactions are shared with multicellular organisms, but due to the incredible diversity of types of microbes these organisms are able to deal with a far wider range of xenobiotics than multicellular organisms, and can degrade even persistent organic pollutants such as organochloride compounds. A related problem for aerobic organisms
10251-494: The chloroplast . These protons move back through the membrane as they drive the ATP synthase, as before. The electrons then flow through photosystem I and can then be used to reduce the coenzyme NADP. This coenzyme can enter the Calvin cycle or be recycled for further ATP generation. Anabolism is the set of constructive metabolic processes where the energy released by catabolism is used to synthesize complex molecules. In general,
10404-407: The circulation . These metabolic activities are regulated by several hormones (e.g., insulin , glucagon and epinephrine ). Adipose tissue also secretes the hormone leptin . A variety of chemical and physical techniques are used for the production and processing of fats, both industrially and in cottage or home settings. They include: The pancreatic lipase acts at the ester bond, hydrolyzing
10557-465: The control exerted by this enzyme is the effect that these changes in its activity have on the overall rate of the pathway (the flux through the pathway). For example, an enzyme may show large changes in activity (i.e. it is highly regulated) but if these changes have little effect on the flux of a metabolic pathway, then this enzyme is not involved in the control of the pathway. There are multiple levels of metabolic regulation. In intrinsic regulation,
10710-438: The cytoskeleton , a system of scaffolding that maintains the cell shape. Proteins are also important in cell signaling , immune responses , cell adhesion , active transport across membranes, and the cell cycle . Amino acids also contribute to cellular energy metabolism by providing a carbon source for entry into the citric acid cycle ( tricarboxylic acid cycle ), especially when a primary source of energy, such as glucose ,
10863-402: The last universal common ancestor . This universal ancestral cell was prokaryotic and probably a methanogen that had extensive amino acid, nucleotide, carbohydrate and lipid metabolism. The retention of these ancient pathways during later evolution may be the result of these reactions having been an optimal solution to their particular metabolic problems, with pathways such as glycolysis and
11016-544: The mevalonate pathway produces these compounds from acetyl-CoA, while in plants and bacteria the non-mevalonate pathway uses pyruvate and glyceraldehyde 3-phosphate as substrates. One important reaction that uses these activated isoprene donors is sterol biosynthesis . Here, the isoprene units are joined to make squalene and then folded up and formed into a set of rings to make lanosterol . Lanosterol can then be converted into other sterols such as cholesterol and ergosterol . Organisms vary in their ability to synthesize
11169-492: The nominal and verbal systems. The major change in the nominal morphology since the classical stage was the disuse of the dative case (its functions being largely taken over by the genitive ). The verbal system has lost the infinitive , the synthetically -formed future, and perfect tenses and the optative mood . Many have been replaced by periphrastic ( analytical ) forms. Pronouns show distinctions in person (1st, 2nd, and 3rd), number (singular, dual , and plural in
11322-425: The regulation of the rate of a metabolic reaction, for example in response to changes in the cell's environment or to signals from other cells. The metabolic system of a particular organism determines which substances it will find nutritious and which poisonous . For example, some prokaryotes use hydrogen sulfide as a nutrient, yet this gas is poisonous to animals. The basal metabolic rate of an organism
11475-744: The rumen of these animals. CLA has two double bonds, one in the cis configuration and one in trans , which makes it simultaneously a cis - and a trans -fatty acid. Concerns about trans fatty acids in human diet were raised when they were found to be an unintentional byproduct of the partial hydrogenation of vegetable and fish oils. While these trans fatty acids (popularly called "trans fats") are edible, they have been implicated in many health problems. The hydrogenation process, invented and patented by Wilhelm Normann in 1902, made it possible to turn relatively cheap liquid fats such as whale or fish oil into more solid fats and to extend their shelf-life by preventing rancidification. (The source fat and
11628-403: The stomach and pancreas , and in salivary glands . The amino acids or sugars released by these extracellular enzymes are then pumped into cells by active transport proteins. Carbohydrate catabolism is the breakdown of carbohydrates into smaller units. Carbohydrates are usually taken into cells after they have been digested into monosaccharides such as glucose and fructose . Once inside,
11781-426: The 20 common amino acids. Most bacteria and plants can synthesize all twenty, but mammals can only synthesize eleven nonessential amino acids, so nine essential amino acids must be obtained from food. Some simple parasites , such as the bacteria Mycoplasma pneumoniae , lack all amino acid synthesis and take their amino acids directly from their hosts. All amino acids are synthesized from intermediates in glycolysis,
11934-465: The 3rd millennium BC, or possibly earlier. The earliest written evidence is a Linear B clay tablet found in Messenia that dates to between 1450 and 1350 BC, making Greek the world's oldest recorded living language . Among the Indo-European languages, its date of earliest written attestation is matched only by the now-extinct Anatolian languages . The Greek language is conventionally divided into
12087-855: The AHA estimated that replacement of saturated fat with polyunsaturated fat in the American diet could reduce the risk of cardiovascular diseases by 30%. The consumption of saturated fat is generally considered a risk factor for dyslipidemia —abnormal blood lipid levels, including high total cholesterol, high levels of triglycerides, high levels of low-density lipoprotein (LDL, "bad" cholesterol) or low levels of high-density lipoprotein (HDL, "good" cholesterol). These parameters in turn are believed to be risk indicators for some types of cardiovascular disease. These effects were observed in children too. Several meta-analyses (reviews and consolidations of multiple previously published experimental studies) have confirmed
12240-486: The Greek alphabet since approximately the 9th century BC. It was created by modifying the Phoenician alphabet , with the innovation of adopting certain letters to represent the vowels. The variant of the alphabet in use today is essentially the late Ionic variant, introduced for writing classical Attic in 403 BC. In classical Greek, as in classical Latin, only upper-case letters existed. The lower-case Greek letters were developed much later by medieval scribes to permit
12393-425: The Greek language are often emphasized. Although Greek has undergone morphological and phonological changes comparable to those seen in other languages, never since classical antiquity has its cultural, literary, and orthographic tradition been interrupted to the extent that one can speak of a new language emerging. Greek speakers today still tend to regard literary works of ancient Greek as part of their own rather than
12546-491: The Greek language was the Cypriot syllabary (also a descendant of Linear A via the intermediate Cypro-Minoan syllabary ), which is closely related to Linear B but uses somewhat different syllabic conventions to represent phoneme sequences. The Cypriot syllabary is attested in Cyprus from the 11th century BC until its gradual abandonment in the late Classical period, in favor of the standard Greek alphabet. Greek has been written in
12699-629: The Greek verb have likewise remained largely the same over the course of the language's history but with significant changes in the number of distinctions within each category and their morphological expression. Greek verbs have synthetic inflectional forms for: Many aspects of the syntax of Greek have remained constant: verbs agree with their subject only, the use of the surviving cases is largely intact (nominative for subjects and predicates, accusative for objects of most verbs and many prepositions, genitive for possessors), articles precede nouns, adpositions are largely prepositional, relative clauses follow
12852-661: The Greek-Albanian border. A significant percentage of Albania's population has knowledge of the Greek language due in part to the Albanian wave of immigration to Greece in the 1980s and '90s and the Greek community in the country. Prior to the Greco-Turkish War and the resulting population exchange in 1923 a very large population of Greek-speakers also existed in Turkey , though very few remain today. A small Greek-speaking community
13005-571: The U.S. Food and Drug Administration , for example, recommends to consume at least 10% (7% for high-risk groups) of calories from saturated fat, with an average of 30% (or less) of total calories from all fat. A general 7% limit was recommended also by the American Heart Association (AHA) in 2006. The WHO/FAO report also recommended replacing fats so as to reduce the content of myristic and palmitic acids, specifically. The so-called Mediterranean diet , prevalent in many countries in
13158-716: The United States and Europe recommend that pregnant and lactating women consume higher amounts of polyunsaturated fats than the general population to enhance the DHA status of the fetus and newborn. In nature, unsaturated fatty acids generally have double bonds in cis configuration (with the adjacent C–C bonds on the same side) as opposed to trans . Nevertheless, trans fatty acids (TFAs) occur in small amounts in meat and milk of ruminants (such as cattle and sheep), typically 2–5% of total fat. Natural TFAs, which include conjugated linoleic acid (CLA) and vaccenic acid , originate in
13311-404: The acute during the late 20th century, and it has only been retained in typography . After the writing reform of 1982, most diacritics are no longer used. Since then, Greek has been written mostly in the simplified monotonic orthography (or monotonic system), which employs only the acute accent and the diaeresis. The traditional system, now called the polytonic orthography (or polytonic system),
13464-402: The ancient language; singular and plural alone in later stages), and gender (masculine, feminine, and neuter), and decline for case (from six cases in the earliest forms attested to four in the modern language). Nouns, articles, and adjectives show all the distinctions except for a person. Both attributive and predicative adjectives agree with the noun. The inflectional categories of
13617-436: The blood. Various tissues can capture the chylomicrons, releasing the triglycerides to be used as a source of energy. Liver cells can synthesize and store triglycerides. When the body requires fatty acids as an energy source, the hormone glucagon signals the breakdown of the triglycerides by hormone-sensitive lipase to release free fatty acids. As the brain cannot utilize fatty acids as an energy source (unless converted to
13770-406: The bond and "releasing" the fatty acid. In triglyceride form, lipids cannot be absorbed by the duodenum . Fatty acids, monoglycerides (one glycerol, one fatty acid), and some diglycerides are absorbed by the duodenum, once the triglycerides have been broken down. In the intestine , following the secretion of lipases and bile , triglycerides are split into monoacylglycerol and free fatty acids in
13923-428: The brain that cannot metabolize fatty acids. In other organisms such as plants and bacteria, this metabolic problem is solved using the glyoxylate cycle , which bypasses the decarboxylation step in the citric acid cycle and allows the transformation of acetyl-CoA to oxaloacetate , where it can be used for the production of glucose. Other than fat, glucose is stored in most tissues, as an energy resource available within
14076-437: The cell for energy. M. tuberculosis can also grow on the lipid cholesterol as a sole source of carbon, and genes involved in the cholesterol-use pathway(s) have been validated as important during various stages of the infection lifecycle of M. tuberculosis . Amino acids are either used to synthesize proteins and other biomolecules, or oxidized to urea and carbon dioxide to produce energy. The oxidation pathway starts with
14229-512: The cells is called intermediary (or intermediate) metabolism. Metabolic reactions may be categorized as catabolic —the breaking down of compounds (for example, of glucose to pyruvate by cellular respiration ); or anabolic —the building up ( synthesis ) of compounds (such as proteins, carbohydrates, lipids, and nucleic acids). Usually, catabolism releases energy, and anabolism consumes energy. The chemical reactions of metabolism are organized into metabolic pathways , in which one chemical
14382-438: The citric acid cycle producing their end products highly efficiently and in a minimal number of steps. The first pathways of enzyme-based metabolism may have been parts of purine nucleotide metabolism, while previous metabolic pathways were a part of the ancient RNA world . Many models have been proposed to describe the mechanisms by which novel metabolic pathways evolve. These include the sequential addition of novel enzymes to
14535-415: The citric acid cycle, or the pentose phosphate pathway. Nitrogen is provided by glutamate and glutamine . Nonessensial amino acid synthesis depends on the formation of the appropriate alpha-keto acid, which is then transaminated to form an amino acid. Amino acids are made into proteins by being joined in a chain of peptide bonds . Each different protein has a unique sequence of amino acid residues: this
14688-632: The coenzyme nicotinamide adenine dinucleotide (NAD) into NADH. Macromolecules cannot be directly processed by cells. Macromolecules must be broken into smaller units before they can be used in cell metabolism. Different classes of enzymes are used to digest these polymers. These digestive enzymes include proteases that digest proteins into amino acids, as well as glycoside hydrolases that digest polysaccharides into simple sugars known as monosaccharides . Microbes simply secrete digestive enzymes into their surroundings, while animals only secrete these enzymes from specialized cells in their guts , including
14841-533: The complex molecules that make up cellular structures are constructed step-by-step from smaller and simpler precursors. Anabolism involves three basic stages. First, the production of precursors such as amino acids , monosaccharides , isoprenoids and nucleotides , secondly, their activation into reactive forms using energy from ATP, and thirdly, the assembly of these precursors into complex molecules such as proteins , polysaccharides , lipids and nucleic acids . Anabolism in organisms can be different according to
14994-487: The construction of cells and tissues, or on breaking them down and using them to obtain energy, by their digestion. These biochemicals can be joined to make polymers such as DNA and proteins , essential macromolecules of life. Proteins are made of amino acids arranged in a linear chain joined by peptide bonds . Many proteins are enzymes that catalyze the chemical reactions in metabolism. Other proteins have structural or mechanical functions, such as those that form
15147-404: The early 19th century that was used for literary and official purposes in the newly formed Greek state. In 1976, Dimotiki was declared the official language of Greece, after having incorporated features of Katharevousa and thus giving birth to Standard Modern Greek , used today for all official purposes and in education . The historical unity and continuing identity between the various stages of
15300-444: The electrons removed from organic molecules in areas such as the citric acid cycle are transferred to oxygen and the energy released is used to make ATP. This is done in eukaryotes by a series of proteins in the membranes of mitochondria called the electron transport chain . In prokaryotes , these proteins are found in the cell's inner membrane . These proteins use the energy from reduced molecules like NADH to pump protons across
15453-433: The elimination of metabolic wastes . These enzyme -catalyzed reactions allow organisms to grow and reproduce, maintain their structures , and respond to their environments. The word metabolism can also refer to the sum of all chemical reactions that occur in living organisms, including digestion and the transportation of substances into and between different cells, in which case the above described set of reactions within
15606-680: The end of the reaction catalyzed. Metal micronutrients are taken up into organisms by specific transporters and bind to storage proteins such as ferritin or metallothionein when not in use. Catabolism is the set of metabolic processes that break down large molecules. These include breaking down and oxidizing food molecules. The purpose of the catabolic reactions is to provide the energy and components needed by anabolic reactions which build molecules. The exact nature of these catabolic reactions differ from organism to organism, and organisms can be classified based on their sources of energy, hydrogen, and carbon (their primary nutritional groups ), as shown in
15759-468: The enzyme that makes it. These enzymes are regulated in a reciprocal fashion, with phosphorylation inhibiting glycogen synthase, but activating phosphorylase. Insulin causes glycogen synthesis by activating protein phosphatases and producing a decrease in the phosphorylation of these enzymes. The central pathways of metabolism described above, such as glycolysis and the citric acid cycle, are present in all three domains of living things and were present in
15912-602: The epics of Homer , ancient Greek literature includes many works of lasting importance in the European canon . Greek is also the language in which many of the foundational texts in science and philosophy were originally composed. The New Testament of the Christian Bible was also originally written in Greek. Together with the Latin texts and traditions of the Roman world , the Greek texts and Greek societies of antiquity constitute
16065-647: The exchange of electrolytes between the extracellular fluid and the cell's fluid, the cytosol . Electrolytes enter and leave cells through proteins in the cell membrane called ion channels . For example, muscle contraction depends upon the movement of calcium, sodium and potassium through ion channels in the cell membrane and T-tubules . Transition metals are usually present as trace elements in organisms, with zinc and iron being most abundant of those. Metal cofactors are bound tightly to specific sites in proteins; although enzyme cofactors can be modified during catalysis, they always return to their original state by
16218-722: The fat it requires from other food ingredients, except for a few essential fatty acids that must be included in the diet. Dietary fats are also the carriers of some flavor and aroma ingredients and vitamins that are not water-soluble . In humans and many animals, fats serve both as energy sources and as stores for energy in excess of what the body needs immediately. Each gram of fat when burned or metabolized releases about nine food calories (37 kJ = 8.8 kcal ). Fats are also sources of essential fatty acids , an important dietary requirement. Vitamins A , D , E , and K are fat-soluble, meaning they can only be digested, absorbed, and transported in conjunction with fats. Fats play
16371-414: The fatty acids are broken down by beta oxidation to release acetyl-CoA, which then is fed into the citric acid cycle. Fatty acids release more energy upon oxidation than carbohydrates. Steroids are also broken down by some bacteria in a process similar to beta oxidation, and this breakdown process involves the release of significant amounts of acetyl-CoA, propionyl-CoA, and pyruvate, which can all be used by
16524-484: The first stage, large organic molecules, such as proteins , polysaccharides or lipids , are digested into their smaller components outside cells. Next, these smaller molecules are taken up by cells and converted to smaller molecules, usually acetyl coenzyme A (acetyl-CoA), which releases some energy. Finally, the acetyl group on acetyl-CoA is oxidized to water and carbon dioxide in the citric acid cycle and electron transport chain , releasing more energy while reducing
16677-490: The focus in future studies. This advice is often oversimplified by labeling the two kinds of fats as bad fats and good fats , respectively. However, since the fats and oils in most natural and traditionally processed foods contain both unsaturated and saturated fatty acids, the complete exclusion of saturated fat is unrealistic and possibly unwise. For instance, some foods rich in saturated fat, such as coconut and palm oil, are an important source of cheap dietary calories for
16830-452: The following periods: In the modern era, the Greek language entered a state of diglossia : the coexistence of vernacular and archaizing written forms of the language. What came to be known as the Greek language question was a polarization between two competing varieties of Modern Greek: Dimotiki , the vernacular form of Modern Greek proper, and Katharevousa , meaning 'purified', a compromise between Dimotiki and Ancient Greek developed in
16983-402: The form of water-soluble messengers such as hormones and growth factors and are detected by specific receptors on the cell surface. These signals are then transmitted inside the cell by second messenger systems that often involved the phosphorylation of proteins. A very well understood example of extrinsic control is the regulation of glucose metabolism by the hormone insulin . Insulin
17136-408: The incidence of insulin resistance ; PUFAs (especially large amounts of arachidonic acid ) and SFAs (such as arachidic acid ) increased it. These ratios can be indexed in the phospholipids of human skeletal muscle and in other tissues as well. This relationship between dietary fats and insulin resistance is presumed secondary to the relationship between insulin resistance and inflammation , which
17289-439: The infinitive entirely (employing a raft of new periphrastic constructions instead) and uses participles more restrictively. The loss of the dative led to a rise of prepositional indirect objects (and the use of the genitive to directly mark these as well). Ancient Greek tended to be verb-final, but neutral word order in the modern language is VSO or SVO. Modern Greek inherits most of its vocabulary from Ancient Greek, which in turn
17442-463: The late 15th century BC, was the first script used to write Greek. It is basically a syllabary , which was finally deciphered by Michael Ventris and John Chadwick in the 1950s (its precursor, Linear A , has not been deciphered and most likely encodes a non-Greek language). The language of the Linear B texts, Mycenaean Greek , is the earliest known form of Greek. Another similar system used to write
17595-527: The major route of breakdown is glycolysis , in which glucose is converted into pyruvate . This process generates the energy-conveying molecule NADH from NAD, and generates ATP from ADP for use in powering many processes within the cell. Pyruvate is an intermediate in several metabolic pathways, but the majority is converted to acetyl-CoA and fed into the citric acid cycle , which enables more ATP production by means of oxidative phosphorylation . This oxidation consumes molecular oxygen and releases water and
17748-504: The majority of the carbon and nitrogen; most of the oxygen and hydrogen is present as water. The abundant inorganic elements act as electrolytes . The most important ions are sodium , potassium , calcium , magnesium , chloride , phosphate and the organic ion bicarbonate . The maintenance of precise ion gradients across cell membranes maintains osmotic pressure and pH . Ions are also critical for nerve and muscle function, as action potentials in these tissues are produced by
17901-676: The mechanisms of carbon fixation are more diverse. Here, carbon dioxide can be fixed by the Calvin–Benson cycle, a reversed citric acid cycle, or the carboxylation of acetyl-CoA. Prokaryotic chemoautotrophs also fix CO 2 through the Calvin–Benson cycle, but use energy from inorganic compounds to drive the reaction. In carbohydrate anabolism, simple organic acids can be converted into monosaccharides such as glucose and then used to assemble polysaccharides such as starch . The generation of glucose from compounds like pyruvate , lactate , glycerol , glycerate 3-phosphate and amino acids
18054-621: The membership of Greece and Cyprus in the European Union, Greek is one of the organization's 24 official languages . Greek is recognized as a minority language in Albania, and used co-officially in some of its municipalities, in the districts of Gjirokastër and Sarandë . It is also an official minority language in the regions of Apulia and Calabria in Italy. In the framework of the European Charter for Regional or Minority Languages , Greek
18207-504: The merits of substituting polyunsaturated fats for saturated fats. The effect of saturated fat on cardiovascular disease has been extensively studied. The general consensus is that there is evidence of moderate-quality of a strong, consistent, and graded relationship between saturated fat intake, blood cholesterol levels, and the incidence of cardiovascular disease. The relationships are accepted as causal, including by many government and medical organizations. A 2017 review by
18360-480: The metabolic pathway self-regulates to respond to changes in the levels of substrates or products; for example, a decrease in the amount of product can increase the flux through the pathway to compensate. This type of regulation often involves allosteric regulation of the activities of multiple enzymes in the pathway. Extrinsic control involves a cell in a multicellular organism changing its metabolism in response to signals from other cells. These signals are usually in
18513-441: The modern period. The division into conventional periods is, as with all such periodizations, relatively arbitrary, especially because, in all periods, Ancient Greek has enjoyed high prestige, and the literate borrowed heavily from it. Across its history, the syllabic structure of Greek has varied little: Greek shows a mixed syllable structure, permitting complex syllabic onsets but very restricted codas. It has only oral vowels and
18666-510: The most abundant biological molecules, and fill numerous roles, such as the storage and transport of energy ( starch , glycogen ) and structural components ( cellulose in plants, chitin in animals). The basic carbohydrate units are called monosaccharides and include galactose , fructose , and most importantly glucose . Monosaccharides can be linked together to form polysaccharides in almost limitless ways. The two nucleic acids, DNA and RNA , are polymers of nucleotides . Each nucleotide
18819-419: The nature of photosynthetic pigment present, with most photosynthetic bacteria only having one type, while plants and cyanobacteria have two. In plants, algae, and cyanobacteria, photosystem II uses light energy to remove electrons from water, releasing oxygen as a waste product. The electrons then flow to the cytochrome b6f complex , which uses their energy to pump protons across the thylakoid membrane in
18972-399: The noun they modify and relative pronouns are clause-initial. However, the morphological changes also have their counterparts in the syntax, and there are also significant differences between the syntax of the ancient and that of the modern form of the language . Ancient Greek made great use of participial constructions and of constructions involving the infinitive, and the modern variety lacks
19125-1054: The object of much study, and are still highly controversial topics. There are two essential fatty acids (EFAs) in human nutrition: alpha-Linolenic acid (an omega-3 fatty acid ) and linoleic acid (an omega-6 fatty acid ). The adult body can synthesize other lipids that it needs from these two. Different foods contain different amounts of fat with different proportions of saturated and unsaturated fatty acids. Some animal products, like beef and dairy products made with whole or reduced fat milk like yogurt , ice cream , cheese and butter have mostly saturated fatty acids (and some have significant contents of dietary cholesterol ). Other animal products, like pork , poultry , eggs , and seafood have mostly unsaturated fats. Industrialized baked goods may use fats with high unsaturated fat contents as well, especially those containing partially hydrogenated oils , and processed foods that are deep-fried in hydrogenated oil are high in saturated fat content. Plants and fish oil generally contain
19278-521: The objects of study of the discipline of Classics . During antiquity , Greek was by far the most widely spoken lingua franca in the Mediterranean world . It eventually became the official language of the Byzantine Empire and developed into Medieval Greek . In its modern form , Greek is the official language of Greece and Cyprus and one of the 24 official languages of the European Union . It
19431-416: The observed health impact of replacing dietary saturated fat with linoleic acid found that it increased rates of death from all causes, coronary heart disease, and cardiovascular disease. These studies have been disputed by many scientists, and the consensus in the medical community is that saturated fat and cardiovascular disease are closely related. Still, these discordant studies fueled debate over
19584-508: The offending substances can be metabolized or removed from the body by such means as excretion , urination , accidental or intentional bloodletting , sebum excretion, and hair growth. In animals, adipose tissue , or fatty tissue is the body's means of storing metabolic energy over extended periods of time. Adipocytes (fat cells) store fat derived from the diet and from liver metabolism . Under energy stress these cells may degrade their stored fat to supply fatty acids and also glycerol to
19737-706: The older periods of Greek, loanwords into Greek acquired Greek inflections, thus leaving only a foreign root word. Modern borrowings (from the 20th century on), especially from French and English, are typically not inflected; other modern borrowings are derived from Albanian , South Slavic ( Macedonian / Bulgarian ) and Eastern Romance languages ( Aromanian and Megleno-Romanian ). Greek words have been widely borrowed into other languages, including English. Example words include: mathematics , physics , astronomy , democracy , philosophy , athletics , theatre, rhetoric , baptism , evangelist , etc. Moreover, Greek words and word elements continue to be productive as
19890-408: The pathway. Terpenes and isoprenoids are a large class of lipids that include the carotenoids and form the largest class of plant natural products . These compounds are made by the assembly and modification of isoprene units donated from the reactive precursors isopentenyl pyrophosphate and dimethylallyl pyrophosphate . These precursors can be made in different ways. In animals and archaea,
20043-780: The pathway. An alternative model comes from studies that trace the evolution of proteins' structures in metabolic networks, this has suggested that enzymes are pervasively recruited, borrowing enzymes to perform similar functions in different metabolic pathways (evident in the MANET database ) These recruitment processes result in an evolutionary enzymatic mosaic. A third possibility is that some parts of metabolism might exist as "modules" that can be reused in different pathways and perform similar functions on different molecules. Greek language Greek ( Modern Greek : Ελληνικά , romanized : Elliniká , [eliniˈka] ; Ancient Greek : Ἑλληνική , romanized : Hellēnikḗ )
20196-575: The pattern was reversed: the Hungarian product containing twice the trans fat of the New York product. Even within the United States, there was variation, with fries in New York containing 30% more trans fat than those from Atlanta . Numerous studies have found that consumption of TFAs increases risk of cardiovascular disease. The Harvard School of Public Health advises that replacing TFAs and saturated fats with cis monounsaturated and polyunsaturated fats
20349-672: The precursor nucleoside inosine monophosphate, which is synthesized using atoms from the amino acids glycine , glutamine , and aspartic acid , as well as formate transferred from the coenzyme tetrahydrofolate . Pyrimidines , on the other hand, are synthesized from the base orotate , which is formed from glutamine and aspartate. All organisms are constantly exposed to compounds that they cannot use as foods and that would be harmful if they accumulated in cells, as they have no metabolic function. These potentially damaging compounds are called xenobiotics . Xenobiotics such as synthetic drugs , natural poisons and antibiotics are detoxified by
20502-432: The process were initially kept secret to avoid consumer distaste. ) This process was widely adopted by the food industry in the early 1900s; first for the production of margarine , a replacement for butter and shortening, and eventually for various other fats used in snack food, packaged baked goods, and deep fried products. Full hydrogenation of a fat or oil produces a fully saturated fat. However, hydrogenation generally
20655-428: The removal of the amino group by a transaminase . The amino group is fed into the urea cycle , leaving a deaminated carbon skeleton in the form of a keto acid . Several of these keto acids are intermediates in the citric acid cycle, for example α- ketoglutarate formed by deamination of glutamate . The glucogenic amino acids can also be converted into glucose, through gluconeogenesis . In oxidative phosphorylation,
20808-491: The risk of cardiovascular diseases, overall cancer incidence, neurodegenerative diseases, diabetes, and mortality rate. A 2018 review showed that a Mediterranean-like diet may improve overall health status, such as reduced risk of non-communicable diseases. It also may reduce the social and economic costs of diet-related illnesses. A small number of contemporary reviews have challenged this negative view of saturated fats. For example, an evaluation of evidence from 1966 to 1973 of
20961-532: The same membranes was inversely associated with breast cancer risk. MUFAs and low SI in erythrocyte membranes are predictors of postmenopausal breast cancer. Both of these variables depend on the activity of the enzyme delta-9 desaturase (Δ9-d). Results from observational clinical trials on PUFA intake and cancer have been inconsistent and vary by numerous factors of cancer incidence, including gender and genetic risk. Some studies have shown associations between higher intakes and/or blood levels of omega-3 PUFAs and
21114-626: The source of constructed molecules in their cells. Autotrophs such as plants can construct the complex organic molecules in their cells such as polysaccharides and proteins from simple molecules like carbon dioxide and water. Heterotrophs , on the other hand, require a source of more complex substances, such as monosaccharides and amino acids, to produce these complex molecules. Organisms can be further classified by ultimate source of their energy: photoautotrophs and photoheterotrophs obtain energy from light, whereas chemoautotrophs and chemoheterotrophs obtain energy from oxidation reactions. Photosynthesis
21267-437: The stressed vowel; the so-called breathing marks ( rough and smooth breathing ), originally used to signal presence or absence of word-initial /h/; and the diaeresis , used to mark the full syllabic value of a vowel that would otherwise be read as part of a diphthong. These marks were introduced during the course of the Hellenistic period. Actual usage of the grave in handwriting saw a rapid decline in favor of uniform usage of
21420-422: The substrate can be acceptors, the polysaccharides produced can have straight or branched structures. The polysaccharides produced can have structural or metabolic functions themselves, or be transferred to lipids and proteins by the enzymes oligosaccharyltransferases . Fatty acids are made by fatty acid synthases that polymerize and then reduce acetyl-CoA units. The acyl chains in the fatty acids are extended by
21573-824: The table below. Organic molecules are used as a source of hydrogen atoms or electrons by organotrophs , while lithotrophs use inorganic substrates. Whereas phototrophs convert sunlight to chemical energy , chemotrophs depend on redox reactions that involve the transfer of electrons from reduced donor molecules such as organic molecules , hydrogen , hydrogen sulfide or ferrous ions to oxygen , nitrate or sulfate . In animals, these reactions involve complex organic molecules that are broken down to simpler molecules, such as carbon dioxide and water. Photosynthetic organisms, such as plants and cyanobacteria , use similar electron-transfer reactions to store energy absorbed from sunlight. The most common set of catabolic reactions in animals can be separated into three main stages. In
21726-463: The three main macronutrient groups in human diet , along with carbohydrates and proteins , and the main components of common food products like milk , butter , tallow , lard , salt pork , and cooking oils . They are a major and dense source of food energy for many animals and play important structural and metabolic functions in most living beings, including energy storage, waterproofing, and thermal insulation . The human body can produce
21879-406: The tissue through glycogenesis which was usually being used to maintained glucose level in blood. Polysaccharides and glycans are made by the sequential addition of monosaccharides by glycosyltransferase from a reactive sugar-phosphate donor such as uridine diphosphate glucose (UDP-Glc) to an acceptor hydroxyl group on the growing polysaccharide. As any of the hydroxyl groups on the ring of
22032-946: The total fat in those foods containing man-made trans fats formed by partially hydrogenating plant fats may be trans fat. Baking shortenings, unless reformulated, contain around 30% trans fats compared to their total fats. High-fat dairy products such as butter contain about 4%. Margarines not reformulated to reduce trans fats may contain up to 15% trans fat by weight, but some reformulated ones are less than 1% trans fat. High levels of TFAs have been recorded in popular "fast food" meals. An analysis of samples of McDonald's French fries collected in 2004 and 2005 found that fries served in New York City contained twice as much trans fat as in Hungary , and 28 times as much as in Denmark , where trans fats are restricted. For Kentucky Fried Chicken products,
22185-480: The transfer of heat and work . The second law of thermodynamics states that in any isolated system , the amount of entropy (disorder) cannot decrease. Although living organisms' amazing complexity appears to contradict this law, life is possible as all organisms are open systems that exchange matter and energy with their surroundings. Living systems are not in equilibrium , but instead are dissipative systems that maintain their state of high complexity by causing
22338-632: The walls of blood vessels called lipoprotein lipases must break down triglycerides into free fatty acids and glycerol. Fatty acids can then be taken up by cells via fatty acid transport proteins (FATPs). Triglycerides, as major components of very-low-density lipoprotein (VLDL) and chylomicrons , play an important role in metabolism as energy sources and transporters of dietary fat. They contain more than twice as much energy (approximately 9 kcal/g or 38 kJ /g) as carbohydrates (approximately 4 kcal/g or 17 kJ/g). The most common type of fat, in human diet and most living beings,
22491-463: The waste product carbon dioxide. When oxygen is lacking, or when pyruvate is temporarily produced faster than it can be consumed by the citric acid cycle (as in intense muscular exertion), pyruvate is converted to lactate by the enzyme lactate dehydrogenase , a process that also oxidizes NADH back to NAD for re-use in further glycolysis, allowing energy production to continue. The lactate is later converted back to pyruvate for ATP production where energy
22644-568: Was a distinct dialect of Greek itself. Aside from the Macedonian question, current consensus regards Phrygian as the closest relative of Greek, since they share a number of phonological, morphological and lexical isoglosses , with some being exclusive between them. Scholars have proposed a Graeco-Phrygian subgroup out of which Greek and Phrygian originated. Among living languages, some Indo-Europeanists suggest that Greek may be most closely related to Armenian (see Graeco-Armenian ) or
22797-549: Was also used as the official language of government and religion in the Christian Nubian kingdoms , for most of their history. Greek, in its modern form, is the official language of Greece, where it is spoken by almost the entire population. It is also the official language of Cyprus (nominally alongside Turkish ) and the British Overseas Territory of Akrotiri and Dhekelia (alongside English ). Because of
22950-546: Was also used in Ancient Greek. Greek has occasionally been written in the Latin script , especially in areas under Venetian rule or by Greek Catholics . The term Frankolevantinika / Φραγκολεβαντίνικα applies when the Latin script is used to write Greek in the cultural ambit of Catholicism (because Frankos / Φράγκος is an older Greek term for West-European dating to when most of (Roman Catholic Christian) West Europe
23103-781: Was interrupted before completion, to yield a fat product with specific melting point, hardness, and other properties. Partial hydrogenation turns some of the cis double bonds into trans bonds by an isomerization reaction . The trans configuration is favored because it is the lower energy form. This side reaction accounts for most of the trans fatty acids consumed today, by far. An analysis of some industrialized foods in 2006 found up to 30% "trans fats" in artificial shortening, 10% in breads and cake products, 8% in cookies and crackers, 4% in salty snacks, 7% in cake frostings and sweets, and 26% in margarine and other processed spreads. Another 2010 analysis however found only 0.2% of trans fats in margarine and other processed spreads. Up to 45% of
23256-566: Was under the control of the Frankish Empire ). Frankochiotika / Φραγκοχιώτικα (meaning 'Catholic Chiot') alludes to the significant presence of Catholic missionaries based on the island of Chios . Additionally, the term Greeklish is often used when the Greek language is written in a Latin script in online communications. The Latin script is nowadays used by the Greek-speaking communities of Southern Italy . The Yevanic dialect
23409-653: Was written by Romaniote and Constantinopolitan Karaite Jews using the Hebrew Alphabet . In a tradition, that in modern time, has come to be known as Greek Aljamiado , some Greek Muslims from Crete wrote their Cretan Greek in the Arabic alphabet . The same happened among Epirote Muslims in Ioannina . This also happened among Arabic-speaking Byzantine rite Christians in the Levant ( Lebanon , Palestine, and Syria ). This usage
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